FABRICATING

THE SAME

CROSS-REFERENCE TO RELATED APPLICATIONS

5 [0001] This application claims priority of US application 63/420,850 which was filed on October 31, 2022 and which is incorporated herein in its entirety by reference.

TECHNICAL FIELD

[0002] The present disclosure relates to assemblies including features attached to the assembly body using brazing in which the assembly is subsequently coated using a chemical vapor deposition (“CVD”) process and to processes for fabricating such an assembly. Such assemblies may be used, for example, in apparatus for generating extreme ultraviolet (“EUV”) radiation.

BACKGROUND 5 [0003] There are many settings where it may be desired to utilize an assembly having features added to the assembly by brazing. It may be additionally desired, however, to use such assemblies in conditions which are corrosive. In such circumstances, it would be advantageous to be able to provide the assembly with a coating that protects the assembly including the features and the braze alloy used to add the features to the assembly. 0 [0004] For example, EUV radiation having wavelengths of around 50 nm or less (also sometimes referred to as soft x-rays) and including radiation at a wavelength of about 13.5 nm, can be used in photolithography processes to produce extremely small features in substrates such as silicon wafers. Methods for generating EUV radiation include converting a target material to a plasma state. The target material preferably includes at least one element, e.g., xenon, lithium, or tin, with one or5 more emission lines in the EUV portion of the electromagnetic spectrum. The target material can be solid, liquid, or gas. In one such method, often termed laser produced plasma (“LPP”), the required plasma can be produced by using a laser beam to irradiate a target material.

[0005] For this process, the plasma is typically produced in a sealed vessel, e.g., a vacuum chamber, and the resultant EUV radiation is monitored using various types of metrology equipment. The processes used to generate plasma also typically generate undesirable byproducts in the vacuum chamber which can include out-of-band radiation, high energy ions, and debris, e.g., atoms and/or clumps/microdroplets of residual target material.

[0006] The environment within the vacuum chamber is thus inimical to components in the vacuum chamber and also to components in pathways for exhausting gas from the vacuum chamber as5 this gas will contain residual target material. Components in the chamber and in these pathways are susceptible to corrosion from liquid residual target material. This drastically reduces the lifetime of these components, requiring repair or replacement of damaged components. This adds considerable cost and machine downtime. It is therefore advantageous to protect these components with some form of a protective coating.

[0007] As an example, it is often desirable to add heating elements to EUV light source components for the purposes of target material management. These heating elements may be attached by brazing. It is also useful to coat the EUV light source components with a layer of material to protect the components from corrosion caused by exposure to target material.

[0008] One way to apply the coating to the components involves using CVD. Conventionally such a layer or film is applied to the component using CVD before the features, in this example heating elements, are attached using brazing. This is because the process temperatures for typical CVD coating processes are close to the melting (liquidus) temperature of the filler alloy used during brazing, e.g., BNi-2, so that there is a risk of braze alloy reflow during the CVD coating process.

[0009] Adding the features after the protective coating has been applied leaves the features brazed to the component exposed. It would be advantageous to have a process in which the entirety of the component including the features added to the component by brazing can be coated with a layer of a protective material using CVD.

SUMMARY

[0010] The following summary provides an overview of the embodiments. This summary is not an extensive description of all contemplated embodiments and is not intended to identify key or critical elements of any embodiments nor imply limits on the breadth of any or all embodiments. Its sole purpose is to present some concepts relating to one or more embodiments in a concise form as a prelude to the more detailed description that is presented later.

[0011] According to one aspect of an embodiment, there is disclosed a method of fabricating a coated component, the method comprising fabricating a component body comprising a metal, adding at least one feature to the component body by brazing the at least one feature to the component using a braze alloy, and depositing a film on a surface of the component body, a surface of the at least one feature, and a surface of the braze alloy using a chemical vapor deposition process at a deposition temperature which does not exceed a liquidus temperature of the braze alloy.

[0012] The film may be a ceramic film. The film may comprise TiN. Fabricating a component body comprising a metal may comprise using an additive manufacturing technique to form the component body. The additive manufacturing technique may comprise 3D printing. The method may further comprise annealing the component body, gas quenching the component body, and performing a surface treatment on the component body. The surface treatment may comprise sand blasting. The gas quenching may be performed using nitrogen. The feature may comprise a heating element. The metal may comprise stainless steel.

[0013] The braze alloy may comprise a nickel-based braze alloy. The braze alloy may comprise BNi-2. [0014] According to another aspect of an embodiment, there is disclosed a method of fabricating a coated assembly, the method comprising forming an assembly body of stainless steel, annealing and then gas quenching the assembly body, sand blasting the assembly body, brazing heater elements to the assembly body using a braze alloy, and depositing a TiN fdm on the assembly body including the heater elements and the braze alloy using a CVD deposition process conducted at a deposition temperature which does not exceed a liquidus temperature of the braze alloy.

[0015] Forming an assembly body of stainless steel may comprise using 3D printing. The braze alloy may comprise a nickel-based braze alloy. The braze alloy may comprise BNi-2. The annealing is performed at a temperature in a range of about 1030 °C to about 1110 °C for a duration in the range of 60 minutes to 90 minutes. The gas quenching may be performed using nitrogen.

[0016] According to another aspect of an embodiment, there is disclosed an apparatus comprising a metallic body, at least one feature attached to the metallic body with a braze alloy, and a fdm deposited on the metallic steel body, the at least one feature, and the braze alloy using a chemical vapor deposition process.

[0017] The film may be a ceramic film. The film may comprise TiN. The feature may comprise a heating element. The braze alloy may comprise a nickel-based braze alloy. The braze alloy may comprise BNi-2.

[0018] Further embodiments, features, and advantages of the present invention, as well as the structure and operation of the various embodiments are described in detail below with reference to the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the present invention and, together with the description, further serve to explain the principles of the disclosed subject matter and to enable a person skilled in the relevant art(s) to make and use the disclosed subject matter

[0020] FIG. 1 is a schematic, not-to-scale diagram of an overall broad conception for a laser- produced plasma EUV radiation source.

[0021] FIG. 2A is a not-to-scale perspective view of a chamber design for an EUV radiation source according to an aspect of an embodiment.

[0022] FIG. 2B is a not-to-scale front view of a component for an EUV light radiation source as may be used in a vessel and exhaust systems of the EUV radiation source according to an aspect of an embodiment.

[0023] FIG. 2C is a cross section of a portion of the component shown in FIG. 2A taken along line C-C of FIG. 2B.

[0024] FIG. 2D is an enlargement of area D of FIG. 2C.

[0025] FIG. 3 is a schematic diagram of a reactor for depositing a layer on a component according to an aspect of an embodiment.

[0026] FIG. 4A is a not-to-scale view of the area shown in FIG. 2C after a protective layer has been applied using CVD according to an aspect of an embodiment.

[0027] FIG. 4B is a not-to-scale view of the area such as that shown in FIG. 2C after a protective layer has been applied using CVD according to another aspect of an embodiment.

[0028] FIG. 5 is a flowchart for a process of fabricating a coated assembly with brazed features according to an aspect of an embodiment.

[0029] FIG. 6 is a flowchart for a process of fabricating a coated assembly with brazed features according to an aspect of an embodiment.

[0030] Further features and advantages of the disclosed subject matter, as well as the structure and operation of various embodiments of the disclosed subject matter, are described in detail below with reference to the accompanying drawings. It is noted that the disclosed subject matter is not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Additional embodiments will be apparent to persons skilled in the relevant art based on the teachings contained herein.

DESCRIPTION

[0031] Various embodiments are now described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to promote a thorough understanding of one or more embodiments. It may be evident in some or all instances, however, that any embodiment described below can be practiced without adopting the specific design details described below. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate description of one or more embodiments.

[0032] Components and processes such as those described herein may render benefits in a wide range of applications and implementations. For the sake of having a specific nonlimiting example to facilitate description, one such application is in semiconductor photolithography.

[0033] With initial reference to FIG. 1 there is shown a schematic view of an exemplary EUV radiation source, e.g., a laser produced plasma EUV radiation source 10. As shown, the EUV radiation source 10 may include a pulsed or continuous laser source 20, which may for example be a pulsed gas discharge CO2 laser source producing a beam 22 of radiation at 10.6 pm or 1 pm. The laser source 20 delivers its beam 22 to an irradiation site 28 inside a vessel or chamber 26.

[0034] A target material delivery system (not shown) introduces droplets of target material into the interior of chamber 26 to the irradiation site 28 where the target material may be irradiated to produce plasma. Tin will be used as an example of a target material in this description but it will be understood that other materials may be used. The vacuum chamber 26 may be provided with a liner 24. [0035] Continuing with FIG. 1, the radiation source 10 may also include one or more optical elements such as a collector 30. The collector 30 may be a normal incidence reflector, for example, implemented as a multilayer mirror with additional thin barrier layers deposited at each interface to effectively block thermally induced interlayer diffusion. The collector 30 has a central aperture to allow the beam 22 to pass through and reach the irradiation site 28. The collector 30 may be, e.g., in the shape of an ellipsoid that has a first focus at the irradiation site 28 and a second focus at a so-called intermediate point 40 (also called the intermediate focus 40) where the EUV radiation may be output from the EUV radiation source 10 and input to, e.g., an integrated circuit lithography scanner which uses the radiation, for example, to process a silicon wafer workpiece in a known manner.

[0036] In an arrangement such as that shown in FIG. 1 a buffer gas may be introduced into the chamber 26 through, for example, ports 34 to establish gas flows intended to direct tin away from vulnerable surfaces such as the surface of the collector 30. This buffer gas leaves that chamber through various exhausts such as exhaust port 46. As mentioned, this exhausted gas typically contains masses of residual tin.

[0037] FIG. 2A shows a chamber 26 having two exhaust ports 45 and 46. The internal opening for the exhaust port 45 and the external opening for the exhaust port 46 are visible in FIG. 2A. Each of the exhaust ports 45 and 46 is provided with an exhaust port cover not visible in FIG. 2A but shown in FIG. 2B. Specifically, FIG. 2B is a front view of an exhaust port cover 50. As can be seen, the exhaust port cover 50 has a throat 52 in a port cover body 54. Also visible in FIG. 2B is an inner surface 55 of port cover body 54 and the bottom edge 53 of the back side of the port cover body 54 as viewed through the front of the throat 52.

[0038] The components for the exhaust system such as exhaust port cover 50 may be fabricated using any one or combination of conventional techniques. To the extent that these components have complicated shapes it may be advantageous to fabricate such components using additive manufacturing techniques. Additive manufacturing refers to any process in which a product is created by building something up, such as molding, and includes 3D printing. These components may also be fabricated using a combination of parts, some of which are made using additive manufacturing techniques and others being made using other manufacturing techniques. It may also be advantageous to fabricate these components out of a material that is resistant to corrosion such as stainless steel.

[0039] One tin contamination mitigation technique involves heating the cover body 54. This heating may be accomplished by attaching heating elements 56 to the cover body 54 as shown in FIG. 2C. Brazing is one method which may be used to attach the heating elements 56 to the cover body 54. In brazing, a filler alloy is used to attach two parts to one another. This can be seen more clearly in FIG. 2D in which the heating element 56 is attached to the cover body 54 using a brazing filler alloy 60. The braze alloy may be, for example, AWS BNi-2 (N99620) filler metal.

[0040] Also in FIG. 2D it can be seen that the heating element 56 may be composed of a sheath 62 which may be stainless steel, a conductive heating filament 66 which generates heat through ohmic resistance, and a packing material 64 selected to protect the conductive heating filament 66 while at the same time moving heat efficiently from the conductive heating filament 66 to the sheath 62. The packing material 64 may be, for example, magnesium oxide.

[0041] As shown in FIG. 3, after processing steps described more fully below, the exhaust port cover 50 with its attached heating elements 56 is placed in a CVD reactor 70 for coating. As depicted, the CVD reactor 70 typically includes a housing 72 having a load door 74. The CVD reactor 70 may also include a furnace 76 which may be a multi-zone furnace. The CVD reactor 70 also typically includes a gas inlet 78 for introducing reactive and precursor gases into the reactor 70 and a gas outlet 80 for exhausting gases from the reactor 70.

[0042] A suitable material for the protective coating for the exhaust port cover 50 is titanium nitride (TiN). The precursor gases for using CVD to deposit a layer of TiN may include N ₂ mixed with a vapor of liquid TiCl i.

[0043] One challenge in using CVD to deposit a layer of TiN on the surface of an article that has features attached to it by brazing is that the temperatures typically used for such a CVD process are too close to the liquidus temperature of the brazing material. For example, the liquidus temperature of BNi-2 filler alloy is about 998 °C. Typical CVD TiN processes, however, may be carried out at temperatures in the range of about 960 °C to about 980 °C. Employing process temperatures so close to the braze alloy liquidus temperature can cause, for example, the brazing material to reflow undesirably. Here and elsewhere in this description and in the claims, the term “about” used in conjunction with a specified numerical value is intended to encompass all values within typical tolerances of the specified numerical value.

[0044] To overcome this challenge, according to an aspect of an embodiment, the CVD process used to deposit a layer of TiN on the surface of an article that has features attached to it by brazing is carried out at lower than conventional temperatures. Although doing so makes the process take longer, it is nevertheless more expedient and requires less labor than measures that would be needed to protect heating elements attached after the coating is applied such as masking the heating elements. Also, according to an aspect, care is taken during the CVD process to avoid temperature spikes in the reactor by, for example, using a multizone furnace.

[0045] The heating elements are still fully functional after being subjected to the additional heated process step which is required by the CVD coating. This coating process adds considerable lifetime to the entire heated assembly as compared to assemblies in which heaters are not coated with CVD TiN.

[0046] A cross section of a portion of the resulting structure can be seen in FIG. 4A. Along with the surface of the cover body 54, the sheath 62 of the heating element 56 is covered with a protective layer 90 as is brazing material 60. According to an aspect, a protective coating 92 is also formed on the surface of the cover body 54 which is not provided with the heating element 56. [0047] FIG. 4B is similar to FIG. 4A except that in FIG. 4B a channel or groove 94 has been formed in the surface of the cover body 54 to provide for more secure attachment of the heating element 56 to the surface of the cover 54 as well as for improved heat transfer between the heating element 56 and the surface of the cover 54. Also visible in both figures is the packing material 64 and the filament 66 of the heating element 56.

[0048] FIG. 5 is a flowchart for a process for fabricating a coated component having elements attached to its surface by brazing according to an aspect of an embodiment. In a step SI 00 the metallic assembly body is fabricated. As noted above, this step SI 10 may be performed using additive manufacturing. Then, in a step SI 10 the assembly body is annealed. Annealing may be performed, for example, at a temperature in a range of about 1030 °C to about 1110 °C for a duration in the range of 60 minutes to 90 minutes.

[0049] Then, in a step S120, the assembly body is gas quenched. This step may be performed using N ₂ .

[0050] Then, in a next step S130, the surface of the assembly body is subjected to a surface treatment. The surface treatment may be, for example, sand blasting. The sand blasting may include two steps, for example, a first step using aluminum oxide and a second step using zirconium oxide. These steps may be carried out at a pressure, for example, of 2 bar.

[0051] Next, in a step S140, a feature is brazed to the surface of the assembly body. Then, in a step SI 50, a film (coating) is deposited on the assembly including the assembly body, the braze filler alloy, and the feature. The film deposition is performed using CVD having a controlled process temperature that remains safely below the liquidus temperature of the braze filler alloy. Herein, “safely below” means the temperature is sufficiently lower that braze filler alloy reflow will not occur.

[0052] FIG. 6 is also a flowchart for a process for fabricating a coated component having elements attached to its surface by brazing according to an aspect of an embodiment. In a step S200 a stainless steel body for the assembly is fabricated. As mentioned above, this step S200 may be performed using 3D printing. In a step S210 the stainless steel body is annealed.

[0053] In step S220, and the annealed assembly is gas quenched. This step may be performed using N ₂ .

[0054] In a step 230, the surface of the stainless steel body is sandblasted. Then, in a step 240, a heater element is attached to the stainless steel body using brazing. Then, in a step 250, a TiN fdm is deposited on the assembly including the stainless steel body, the heater elements, and the braze alloy using a temperature controlled CVD process as described above. The fdm deposition is performed using CVD having a controlled process temperature that remains safely below the liquidus temperature of the braze fdler alloy. According to an aspect of an embodiment, the temperature for the CVD process is maintained a deposition temperature which does not exceed a liquidus temperature of the braze alloy.

[0055] The above description includes examples of one or more embodiments. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the aforementioned embodiments, but one of ordinary skill in the art may recognize that many further combinations and permutations of various embodiments are possible. Accordingly, the described embodiments are intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims. Furthermore, to the extent that the term “includes” is used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the term “comprising” as “comprising” is construed when employed as a transitional word in a claim. Furthermore, although elements of the described aspects and/or embodiments may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated. Additionally, all or a portion of any aspect and/or embodiment may be utilized with all or a portion of any other aspect and/or embodiment, unless stated otherwise.

[0056] The implementations can be further described using the following clauses.

1. A method of fabricating a coated component, the method comprising: fabricating a component body comprising a metal; adding at least one feature to the component body by brazing the at least one feature to the component using a braze alloy; and depositing a fdm on a surface of the component body, a surface of the at least one feature and, and a surface of the braze alloy using a chemical vapor deposition process at a deposition temperature which does not exceed a liquidus temperature of the braze alloy.

2. The method as in clause 1 wherein the film is a ceramic film.

3. The method as in clause 1 wherein the film comprises TiN.

4. The method as in clause 1 wherein fabricating a component body comprising a metal comprises using an additive manufacturing technique to form the component body.

5. The method as in clause 4 wherein the additive manufacturing technique comprises 3D printing.

6. The method as in clause 1 further comprising, after fabricating the component body and before adding at least one feature to the component body, annealing the component body, gas quenching the component body, and performing a surface treatment on the component body.

7. The method as in clause 6 wherein the surface treatment comprises sand blasting.

8. The method as in clause 6 wherein the gas quenching is performed using nitrogen.

9. The method as in clause 1 wherein the feature comprises a heating element.

10. The method as in clause 1 wherein the metal comprises stainless steel.

11. The method as in clause 1 wherein the braze alloy comprises a nickel-based braze alloy.

12. The method as in clause 1 wherein the braze alloy comprises BNi-2.

13. A method of fabricating a coated assembly, the method comprising: fabricating an assembly body of stainless steel; annealing and then gas quenching the assembly body; sand blasting the assembly body; brazing heater elements to the assembly body using a braze alloy; and depositing a TiN film on the assembly body including the heater elements and the braze alloy using a CVD deposition process conducted at a deposition temperature which does not exceed a liquidus temperature of the braze alloy.

14. The method as in clause 13 wherein forming an assembly body of stainless steel comprises using 3D printing.

15. The method as in clause 13 wherein the braze alloy comprises a nickel-based braze alloy.

16. The method as in clause 13 wherein the braze alloy comprises BNi-2.

17. The method as in clause 13 wherein the annealing is performed at a temperature in a range of about 1030 °C to about 1110 °C for a duration in the range of 60 minutes to 90 minutes.

18. The method as in clause 13, wherein the gas quenching is performed using nitrogen.

19. Apparatus comprising: a metallic body; at least one feature attached to the metallic body with a braze alloy; and a film deposited on the metallic steel body, the at least one feature, and the braze alloy using a chemical vapor deposition process.

20. The apparatus as in clause 19 wherein the fdm is a ceramic fdm.

21. The apparatus as in clause 19 wherein the fdm comprises TiN.

22. The apparatus as in clause 19 wherein the feature comprises a heating element.

23. The apparatus as in clause 19 wherein the braze alloy comprises a nickel-based braze alloy.

24. The apparatus as in clause 19 wherein the braze alloy comprises BNi-2.

[0057] The above described implementations and other implementations are within the scope of the following claims.